On the 60th anniversary of the start of former Chinese leader Mao Zedong’s campaign against intellectuals that saw some half a million people persecuted by the Communist Party, some present-day scholars say there is again growing pressure from the authorities to silence liberal voices.

Since the administration of President Xi Jinping took over in late 2012, the authorities have tightened ideological control over universities and increased censorship of conventional and social media. Academics deemed controversial have had their social media access curtailed while others have left their posts.

“The ideology of mainland China has seriously retrogressed in recent years, with increasing control over intellectuals and the media, and little freedom of speech,” said Hong Zhenkuai, a mainland historian and former executive editor of liberal political magazine Yanhuang Chunqiu.

“The current situation is that liberal intellectuals have been comprehensively suppressed and have lost the right to speak on public media that they used to enjoy during president Hu Jintao’s administration,” Hong said, referring to Xi’s predecessor.

Yanhuang Chunqiu was forced to replace its editorial team with outsiders last year. Hong himself was sued for defamation after he questioned a Communist Party official account of some wartime heroes. He lost the case and was ordered to make a public apology.

Although Xi had attended a meeting in March of several officially sanctioned non-communist political parties, whose members sixty years ago were among those persecuted, and said intellectuals should be trusted and respected and their criticisms welcomed, other academics have found their ability to speak and write sharply curtailed.

He Weifang, a law professor at Peking University, told the Associated Press last month that he would no longer publish on social media after authorities repeatedly shut down his personal blog, his Weibo microblog and two WeChat accounts.

“Obviously, the situation for Chinese intellectuals has become harsher after the 18th National Congress of the Communist Party of China [in late 2012],” He told the Post, referring to the meeting at which Xi Jinping was formally named party leader.

“It can be called the harshest time since 1978,” he said. He has been almost banned from giving guest lectures at mainland universities, and a book he wrote on the restive Muslim Xinjiang region, where there have been terrorist attacks by groups opposed to Beijing’s control, was rejected by mainland publishers and was finally published in Hong Kong.

In April this year Qiao Mu, a former associate professor in mass communication at Beijing Foreign Studies University, announced his resignation. Qiao, who had written on sensitive subjects including censorship, had been removed from his teaching post in 2014 and given a job in the library.

“Why did I resign?” he wrote on his Wechat public account. “A political science PhD can’t talk about democracy and constitutionalism. A journalism professor has to be against a free media.”

To Hong’s mind, recent cases like these are eerie echoes of the Anti-Rightist Movement, a series of campaigns between 1957 and 1958 against those who had spoken out in a previous campaign called the Hundred Flowers Movement, in which the Communist Party had encouraged public criticism.

More than 550,000 people, many of them intellectuals, were labelled as rightists, including former premier Zhu Rongji, who was then working at the state economic planning agency. He was expelled from the party in 1958, but reinstated 20 years later.

According to his book Zhu Rongji on the Record: The Shanghai Years, he had told the city’s legislators in 1988 that he “had not carefully chosen his words” during a three-minute speech in 1957 presenting his suggestions to the planning agency’s party group.

Many of those labelled as rightists had a much harder time, some even dying from hunger or the hard labour they faced when sent to the countryside for re-education.

Mainland-born Hong Kong resident Chan Yu-lam, 81, was labelled a rightist when he was a student at Beijing Foreign Studies University, because the party branch at the college was ordered to find two “rightists”. He was sent to Inner Mongolia for education through labour.

“I could only have rice for a meal three times a year,” he told the South China Morning Post.

“We were living near the Dahei River where dead people and animals came downstream. We buried the dead people and ate the pigs if they did not stink.”

However, some of the academics said that while control has been tightened, the conditions do not exist today for a repeat of the Anti-Rightist Movement. Social changes, including the rise of private enterprise, made it much more difficult for the authorities to control the lives of individual citizens.

“That kind of movement needs several important prerequisites,” said Peking University’s He Weifang.

“Firstly, there must be a leader like Mao Zedong, who was nearly deified; secondly, most citizens should totally believe in the official ideology and agree on the official choice of social system; thirdly, information must be blocked and people must be unable to find out about disagreements and other information [that differs from the official view]. These conditions do not exist today.”